1. Field of the Invention
This invention relates to thin film heads and more particularly to magnetoresistive (MR) thin film heads.
2. Description of Related Art
U.S. Pat. No. 5,435,053 of Krounbi et al. for xe2x80x9cSimplified Method of Making Merged MR Headxe2x80x9d shows a method for making a planarized merged pole.
U.S. Pat. No. 5,639,509 of Schemmel for xe2x80x9cProcess for Forming a Flux Enhanced Magnetic Data Transducerxe2x80x9d shows a two layered bottom pole formed by a top shield composed of an NiFe layer 42 covered with a pole layer 48 for an inductive read head formed of a thin flux enhancement layer with relatively High Magnetic Moment (HMM). As to the NiFe layer 42, ratio of Ni to Fe in the composition is unspecified. This is a flux enhanced data transducer and method for producing the same in conjunction with shared shields on MR read heads. Between 500 xc3x85-2500 xc3x85 of a HMM material 48 is added to the upper surface of the shared shield 42, to form the bottom pole of an inductive write head 40 pole, prior to a magnetic flux containment ion milling operation utilizing the upper pole as a mask. The HMM flux enhancement layer 42, which may be composed of FeN, CoNiFe or other higher magnetic moment materials, is deposited prior to the formation of the dielectric gap layer. The flux enhancement layer may then be selectively removed substantially surrounding the upper pole by means of a relatively brief ion milling process in which only on the order of 1.0 kxc3x85 of the layer needs to be removed and during which only an insignificant amount of the material removed might be re-deposited on the sides of the upper pole.
U.S. Pat. No. 5,750,275 of Katz et al. for xe2x80x9cThin Film Heads with Insulated Laminations for Improved High Frequency Performancexe2x80x9d shows a laminated magnetic pole member using an alumina (Al2O3) insulating layer.
U.S. Pat. No. 5,606,478 of Chen et al. for xe2x80x9cNi45Fe55 Metal-in-Gap Thin Film Magnetic Headxe2x80x9d shows a composite structure with an MR magnetic read head with an MR stripe and an inductive magnetic read head. Between the MR head and the inductive head is a pole piece composed of a combination of High Magnetic Moment (HMM) and PERMALLOY-Like Material (PLM) with Low Magnetic Moment (LMM) laminated together. The MR head includes two magnetic shields with the lower one formed on the substrate. A shared shield/pole includes the upper magnetic shield of the MR head formed in a composite structure with the lower pole of the inductive magnetic read head. The shared PLM shield/HMM pole which is formed of plated thick layer of Ni80Fe20 which is a PLM material/with a plated thin layer of Ni45Fe55 which is an HMM material.
With the continuous trend in the magnetic recording industry towards increasing the track density of magnetic recording, it becomes increasingly important to reduce edge erasure from adjacent track writing. Edge erasure, resulting from writing fringe, can decrease the written track width and can reduce drive yield by degrading off-track capacity and/or unwanted overwriting of adjacent tracks when writing. The writing fringe field often comes from a dimensional inconsistency and a mismatch of materials near the area where the flux is crowded, i.e. the gap area, of write heads. Recording on high-coercivity media especially requires magnetic recording heads made of High Moment Material (HMM) for write poles and PERMALLOY Material (PLM) for MR shields.
Magnetic poles made of materials with a saturation magnetization higher than that of PERMALLOY are desirable for improving the writability of magnetic recording heads.
We have found that there is a need for merged MR recording heads with both High saturation Moment Material (HMM) and PERMALLOY for a shared pole. The HMM material is suitable for recording on high-coercivity media. PERMALLOY or PERMALLOY-Like Material (PLM) can function as a good sensor shield.
Materials with a saturation magnetization higher than that of PERMALLOY (Ni79Fe21 alloy) are desired for improving the writability of recording heads. A considerable need has led towards the direction of producing magnetoresistive (MR) merged recording heads with High saturation Moment (4xcfx80Ms) Material (HMM) and PERMALLOY.
PERMALLOY or PERMALLOY-like materials (PLMs) can function as a good sensor shields. A copending commonly assigned application Ser. No. 09/283,840 filed on Apr. 1, 1999, now U.S. Pat. No. 6,393,692 entitled xe2x80x9cMethod of Manufacture of a Composite Shared Pole Design for MR Merged Heads and Device Manufactured Therebyxe2x80x9d has a shared pole design which minimizes the effects of dimension change and material mismatch on side writing. The subject matter thereof is Incorporated herein by reference.
Due to the improvement of head performance, we find that planarization of a shared pole is useful for flattening topography resulting from MR and conductors.
When using a metal planarization process, it is difficult to obtain good uniformity across the wafer. The variation in thickness can be as large as xc2x10.7 xcexcm which results in large variations in the thickness of the top, HMM layer if the planarization process is to be applied after both the PML layer and the HMM layer were formed. The thickness of the HMM layer is critical for eliminating saturation, which can cause a large writing fringe field.
A method of manufacturing a magnetic recording head includes the following steps. Form a low magnetic moment, first magnetic shield layer (S1) over a substrate.
Form a read gap layer (RG) with a magnetoresistive head over the first shield layer (Si). Then form a seed layer (SL) over the read gap layer (RG). Next, form a frame mask (PR) with width (F) over the seed layer (SL). Form a low magnetic moment, second magnetic shield layer (S2A) over the seed layer (SL), which is over the read gap layer (RG). Planarize the low magnetic moment, second magnetic shield layer (S2A). Preferably, form a non-magnetic spacer metal or metal alloy layer (SP), preferably composed of copper, over the second magnetic shield layer. Then form a lower, first high magnetic moment, lower pole layer (S2B) over the second magnetic shield layer (S2A), preferably over the non-magnetic spacer metal or metal alloy layer (SP).
Then, form a second mask covering a portion of the structure defined by the frame mask. Then, outside of the second frame mask, remove the portions the upper, second high magnetic moment, pole (UP), the write gap layer (WG), the first high magnetic moment, lower pole layer (S2B), the second magnetic shield layer (S2A), and the seed layer (SL).
FIGS. 1A-1I shows successive steps in a process of manufacturing a device shown in FIG. 2 in accordance with the method of this invention. FIG. 1I shows a section taken along line 1xe2x80x941 in FIG. 2. FIGS. 1A-1H show a series of sections taken generally along line 1xe2x80x941 of FIG. 2 in various earlier stages of the process of this invention leading to the device shown in FIGS. 1I and 2.
FIG. 2 shows a fragmentary sectional view of a merged MR head with a PLM shield layer laminated with an HMM lower pole layer in accordance with this invention showing an embodiment of this invention.
Then employ etching, preferably ion beam etching (IBE), to narrow the write gap layer (WG) to the width xe2x80x9cNxe2x80x9d of the second high magnetic moment, upper pole (UP). Also employ etching (preferably IBE) to pattern the first high magnetic moment, lower pole layer to magnetic pole width xe2x80x9cNxe2x80x9d in part and flaring the remainder of the high magnetic moment, lower pole layer (S2B) towards the width xe2x80x9cWxe2x80x9d, where xe2x80x9cWxe2x80x9d is substantially greater than xe2x80x9cNxe2x80x9d, but xe2x80x9cWxe2x80x9d is substantially less than the width of the second magnetic shield layer (S2A).
As a result, the upper, second high magnetic moment, upper pole layer (UP) has a narrow width xe2x80x9cNxe2x80x9d, the high magnetic moment, lower pole layer (S2B) has a width xe2x80x9cNxe2x80x9d underneath the write gap, and the high magnetic moment, lower pole layer (S2B) also has a width xe2x80x9cWxe2x80x9d over the second magnetic shield layer (S2A). Narrow the upper, second pole layer (UP) and the write gap layer (WG) to upper magnetic pole width xe2x80x9cNxe2x80x9d where width xe2x80x9cWxe2x80x9d is substantially greater than width xe2x80x9cNxe2x80x9d, but substantially less than the width of the second shield, and pattern the first high magnetic moment, lower pole layer (S2B) to magnetic pole width xe2x80x9cNxe2x80x9d in part and flaring the remainder of the first high magnetic moment, lower pole layer (S2B) towards the width xe2x80x9cWxe2x80x9d of the second magnetic shield layer (S2A). This structure is fashioned by using the upper pole (UP) as a mask to trim the high magnetic moment, lower pole layer (S2B) (below upper pole (UP)) of the shared lower pole (LP) so that the high magnetic moment, lower pole layer (S2B) has the same dimension xe2x80x9cNxe2x80x9d as the upper pole (UP) and its bottom part is wider with a width xe2x80x9cWxe2x80x9d towards the PLM shield layer (S2A).
Preferably, the low magnetic moment, second magnetic shield layer (S2A) over the read gap layer is formed of a material selected from the group consisting of metals and alloys having soft-magnetic properties including PERMALLOY, NiFeCr, NiFeMo, NiFeW, NiFePd, NiFeCu, ard NiFeCo. Both the lower HMM pole layer (S2B) and the upper HMM pole layer (UP) are formed of a material selected from the group consisting of Ni45Fe55, Ni45 Fe55Sn, CoNiFe, CoFeCu, Ni45Fe55Cr, and Ni45Fe55Mo.
Preferably, sputter a PLM nickel-iron seed layer over the read gap layer prior to plating the low magnetic moment, second magnetic shield layer.
The trimming time can be defined by the thickness of the the first HMM lower pole layer (S2B) and its slope (i.e. from width W to width N over the thickness of the first HMM lower pole layer (S2B)).
This process makes it possible to perform the steps of plating/planarizing/plating/plating which allows us to have planarization variation remain the first plated layer (S2A) of the shared shield and keep the lower pole PLM (S2A) and first HMM lower pole layer (S2B) uniform.
A layered structure such as (PLM/non-magnetic spacer/HMM) can use a process sequence of processing steps of plating/planarization/plating/plating.
A non-magnetic passivation layer such as silicon oxide or ferric hydroxide can be used with processing steps of plating/planarization/passivation/plating.
This shared pole design minimizes the effects of dimension change and material mismatch at the write gap on side writing.